Conventional fuel delivery systems for automotive vehicles typically include a fuel tank pressure sensor, mounted on the fuel tank, to sense the vapor pressure within the tank. This information is relayed to an electronic engine controller so that the controller can determine whether a leak has occurred in the tank, for example, as required by On-Board Diagnostic (OBD II) requirements. In addition, the controller may use the sensed vapor pressure to determine when the tank must be purged. Purged vapor is then vented to the intake manifold of the engine to be consumed therein. Alternatively, the vapor may be stored in a carbon canister.
Prior art pressure sensor and vent valve assemblies, such as that disclosed in U.S. Pat. No. 5,267,470, include a body having a vent port extending into the fuel tank for evacuating purged vapor from the tank and a pressure sensor port communicating with a pressure sensor element for sensing vapor pressure therein. A check valve maybe located within the vent port so that should the vehicle inadvertently roll over, liquid fuel does not flow therethrough.
The inventors of the present invention have found certain disadvantages with these prior art pressure sensor and vent valve assemblies. For example, the pressure sensor and vent valve ports extend beyond the wall of the fuel tank. Thus, should a portion of the assembly shear off, either port may be exposed to the atmosphere resulting in liquid fuel potentially spilling from the fuel tank.
Further, the check valve assembly located within the vent valve may remain in the closed position during normal vehicle operating conditions.
Also, some prior art pressure sensor and vent valve assemblies utilize a check valve within the pressure sensor port. A disadvantage with these assemblies is that this check valve too may remain in the closed position, thereby preventing a proper pressure reading. As a result, the Malfunction Indicator Light (MIL) illuminates requiring the operator to service the vehicle, thereby increasing warranty costs.